Embodiments herein generally relate to sheet feeders and more particularly to sheet feeders used with scanners and transparent platens that use calibration strips.
Imaging units in sheet feeders can be particularly sensitive to cross process magnification errors caused by variation in the gap between the transparent platen and the sheet throughout the feed. Two distinct errors are sometimes produced. The first occurs as the lead edge of the sheet travels past the scan point and follows the paper path to the exit rolls. The second occurs as the trail edge falls from the calibration strip. The severity of the image quality defects is a combination of both the change in the magnitude of the gap between the sheet and transparent platen and the rate at which the gap changes. The cross process magnification errors manifest themselves most as kinks in straight lines at the inboard or outboard extremities of the sheet.